Users of the federal site for Floridians reported difficulty logging in, and waited as long as an hour to speak to representatives who apologetically explained that the system was down. Similar problems were reported around the country, with marketplaces run by the federal government as well as some operated by state governments.

In midday remarks, the president said the main site, healthcare.gov, was running slow because so many people were trying to access it — more than a million before 7 a.m. By late afternoon, officials reported more than 2.8 million visitors, more than the Medicare website had ever received in a single day.

The Obama administration said it was addressing the problems but gave no time line. By 4 p.m., federal officials reported that people had enrolled in plans through the federal exchange, but declined to say how many had signed up or in which states.

Officials emphasized that people have plenty of time to sign up for coverage — the signup deadline for coverage that starts Jan. 1 isn't until Dec. 15. They also called the first day a success because of the Web traffic.

"We are certainly very pleased with the remarkable interest we've seen," said Julie Bataille, communications director for the Centers for Medicare & Medicaid Services.

But many consumers couldn't find out if they qualified for subsidies or even take a peek at the plans' costs or networks.

Later Tuesday, the Obama administration released premium costs of plans for consumers of various ages in each of the nation's counties. In Pinellas, Hillsborough, Pasco and Hernando counties, the list shows 404 available plans, from barebones "catastrophic'' coverage to the most expensive "platinum'' plans that cover an average of 90 percent of medical costs.

For example, a single, 50-year-old has choices ranging from a $167-per-month Humana bronze plan that covers 60 percent of average costs to a $614 Florida Blue platinum plan.

Missing are critical details about out-of-pocket costs and networks needed to make a fully informed decision about coverage. Additionally, consumers also need to apply at healthcare.gov to determine the subsidies they may receive to offset costs.

Locally, plans are offered by Aetna, Cigna, Coventry, Florida Blue (which has the most plans) and Humana.

Some local "navigators" — federally funded workers trained to help consumers sort through their options on the exchange — had customers on Tuesday.

At University of South Florida-based Florida Covering Kids & Families in Tampa, three navigators met with a handful of people and have a dozen more appointments scheduled.

With the website so overwhelmed, navigators spent the time explaining how coverage and subsidies will work and also offered paper applications, which consumers can mail in or use later as a guide if they prefer to use the website.

Jodi Ray, USF project manager, said she wanted to keep the process going until the site is working fully. "I'm not getting sidetracked," she said.

One of the first people in the office was 20-year-old Chris Dawson, a USF senior majoring in public health. He hasn't had insurance in the two years since he aged out of a government plan for children.

While uninsured, Dawson has hurt his ankle and had bronchitis. He has gone to a student health clinic, but has never had his ankle X-rayed.

"The government is not perfect, but it is great to see a movement toward helping people," he said.

Dawson has an $8 an hour tutoring job. After he pays his rent and other expenses, he has only about $70 he can put toward insurance. With his income so low, he may be one of the million Floridians left in a coverage gap by the Legislature's decision not to expand the Medicaid program. The marketplace subsidies are only for people between 100 percent and 400 percent of the federal poverty level.

"It'd be very disappointed (to be in the coverage gap) but at the same time I'm prepared for that," Dawson said.

In a morning conference call with reporters, U.S. Rep. Kathy Castor, D-Tampa, and Ron Pollack, executive director of the advocacy group Families USA, downplayed the glitches.

"Even in the face of all the obstruction, the marketplace is finally open," Castor said. Consumers "don't have to rush right in today and sign up. … This is just the first day of kickoff.''

Insurers also reported an uptick in calls. Humana spokesman Mitch Lubitz attributed part of that surge to the fact that Tuesday was also the first day that Medicare Advantage customers could get information about their 2014 plans.

For weeks, experts — and even Obama himself — have warned that the startup could be rocky.

Then came the government shutdown prompted by anti-Obamacare Republicans in Congress. However, officials said that closing the government would not stop the online health insurance marketplace because it is being operated with funds outside the annual budget fights.

Some have warned that a difficult beginning could doom the success of Obamacare.

But Tampa Bay-area resident Beverly Borrelli, 61, says she can't afford to get discouraged. Borrelli recently lost her job with a Pasco County employer after 26 years of service and has no health insurance. She tried to sign up on the marketplace Tuesday morning, and after getting stuck on the website called the toll-free number.

"It's really critical for me to have coverage, so whatever it takes I will pursue it,'' she said. "I was only on hold for 20 minutes, and the representative was truly polite and very nice,'' though with the system down they couldn't process her application.

But that's not what she found most trying on Tuesday.

"I'm really angry about what I feel is game playing and politics,'' she said of the government shutdown. "So many lives are impacted.''

Times staff writers Charlotte Sutton, Tia Mitchell and Lisa Buie contributed to this report, which also contains information from the Associated Press. Jodie Tillman can be reached at jtillman@tampabay.com or (813) 226-3374.

EDMUND D. FOUNTAIN | Times

University of South Florida student Chris Dawson, 20, who has been without insurance, talks with marketplace navigator Xonjenese Jacobs on Tuesday about the Affordable Care Act.

Certified application counselors are available at local community health centers, including Suncoast Community Health Centers and Tampa Family Health Centers in Hillsborough; Community Health Centers of Pinellas; Premier Community HealthCare Group in Pasco; and Nature Coast Community Health Center in Hernando.